1. Field of the Invention
The present invention relates to a grinder with a generally vertical, rotatable first shaft having at least one set of cutter discs driven thereby and a fan assembly mounted below the cutter blades on a second vertical, rotatable second shaft in position to receive output from the cutter blades. The first and second shafts are driven by separate motors. Other features will be apparent in view of the disclosure which follows.
2. Brief Description of the Prior Art
Grinders, shredders or mills are well known devices for reducing the particle size of a material. For example, U.S. Pat. No. 5,192,029 to Harris, U.S. Pat. No. 5,680,994 to Eide et al. and U.S. Pat. No. 7,950,601 to Watts disclose mills for grinding garbage. Each of these mills includes a rotor mounted in a octagonal housing. The rotor includes a generally vertical shaft and a plurality of blades mounted on the shaft. Garbage is admitted into the housing through an inlet near the top of the housing and is impacted by the blades of the rotor. Material of a reduced particle size is removed from the mill through an outlet near the bottom of the housing.
The mill of Eide et al. '994 and Watts '601 further includes a fan or impeller which is mounted on the same shaft as the cutter discs. The fan is intended to create airflow which acts to move material through the mill and to expel it from the outlet. The airflow from the fan also acts to remove moisture from the material as it is being ground. Since different materials and different grinding conditions produce different moisture levels in the material, it is advantageous if the rate of airflow can be adjusted.
In Watts '601 the airflow can be adjusted by repositioning the fan blades on the fan disc. This, however, requires opening up the grinder to access the fan blades which interferes with production throughput. In addition, the newly positioned blades may not produce the desired airflow and the process may need to be repeated until an acceptable result is achieved. In addition as mentioned above, different materials have different moisture levels and with the Watts '601 grinder it is not possible to adjust the airflow dynamically.